1. Field of Invention
The present invention relates to adsorbent materials having enhanced adsorptive properties and a method for their manufacture.
2. Prior Art
Unwanted impurities such as viruses, bacteria, proteins and metals have been recovered from water using different types of filters and adsorption-elution procedures [Gerba, Advances in Applied Microbiology 30:133-158 (1984); Farrah et al, In: C. P. Gerba and S. M. Goyal (ed.), Methods in Environmental Virology, Marcel Dekker, New York (1982); Farrah et al, Appl. Environ. Microbiol. 31:221-226 (1976); Goyal et al, In: B. J. Dutka (ed.) Membrane Filtration, Marcel Dekker, New York (1981); Hill et al, Water Res. 967-995 (1971); Payment et al, Appl. Environ. Microbiol. 47:591-592 (1984); Singh et al, Appl. Environ. Microbiol. 45:232-237 (1983); Sobsey et al, Can. J. Microbiol. 23:770-778 (1977); Vilagines et al, Can. J. Microbiol. 28:783-787 (1982); Wallis et al, J. Am. Water Wrks. Assoc. 64:189-196 (1972); Wallis et al, J. Am. J. Epidemiology 85:459-468 (1967); Wallis et al, Annu. Rev. Microbiol. 33:413-437 (1979); Liu et al, Appl. Microbiol. 21:405-410 (1971) and Melnick et al, Am. J. Hyg., 59:185-195 (1954)]. The use of filters has permitted recovery of small amounts of impurities from relatively large volumes of water. Impurities can also be recovered from solutions by adsorption to insoluble precipitates of metallic ions. In particular, insoluble salts of aluminum, calcium, and magnesium have been found to efficiently adsorb a variety of contaminants.
Ferric chloride has been used to enhance the formation of virus-adsorbing flocs in solutions that have been used to elute viruses adsorbed in membrane filters. These flocs and precipitates have been formed in relatively small volumes of water or other liquid and collected by centrifugation or filtration. The need to use centrifugation and the limited capacity of filters to collect flocs before clogging has limited the volume of water that can be easily sampled using these flocs for virus adsorption. Since certain insoluble salts efficiently adsorb viruses at pH values near neutrality, attempts have been made to use flocs trapped on filters to concentrate viruses from large volumes of water using flow-through systems. See U.S. Pat. Nos. 4,048,028; 3,816,304; Myagkii, Chem. Abs., Vol. 100, 161369a (1984); Hou, Chem. Abs., Vol. 100, 126947R (1984) and Homma et al, Chem. Abs., Vol. 83, 91749d (1975), Seeley and Primrose, J. Appl. Bac., Vol. 46, p. 103 (1979).
These attempts have been unsuccessful, however, because filters with large pores did not retain the flocs whereas filters with pores small enough to retain the flocs rapidly became clogged during the filtration procedure.
Gerba et al [J. Environ. Sci. Health, A23:41-58 (1988)] describes a system for inactivating bacteria in an aqueous medium by passing the latter through a filter constructed from a slurry of cellulose fibers and magnesium peroxide. This process and system, however, are limited to filters that have magnesium peroxide incorporated therein during the manufacturing process. There exists a need in the art for a system which permits modification of pre-formed filters to enhance their adsorptive capacity.
Silver and other heavy metals are effective antimicrobial agents and have been used in medicine for such purposes for many years. Conventionally, solutions of salts of the metals are applied topically to the area of treatment. A major disadvantage of this type of procedure is the requirement for frequent applications of the treating reagents.
Deitch et al, Antimicrob. Agents Chemother., Vol. 23, pp. 356-359 (1983) developed nylon coated with metallic silver for use as a bandage. Fabrics composed of silver nylon cloth have been found to possess antimicrobial activity in vitro and in vivo [Deitch et al, J. Trauma, Vol. 27, pp. 301-304 (1987)].
Geldreich et al, Jour. AWWA, Vol. 27, pp. 72-80 (1985) and Reasoner et al, J. AWWA, Vol. 79, pp. 60-66 (1987) studied several commercially available granular activated carbon (GAC) filters with and without impregnated silver; however, none of the products consistently provided water with low bacterial counts.
It is an object of the present invention to provide adsorbent materials having enhanced adsorptive properties which are not subject to the above-noted disadvantages and methods for their manufacture and methods for their utilization as adsorptive and antimicrobial materials.